Such lifting beam automatics or assemblies are known and include transport beams which grasp workpieces between them and execute a longitudinal movement, a lifting and lowering vertical movement and a transverse movement. Gear devices controlled by a switching device are used to effect the desired movement.
In known forming presses having automatic workpiece transportation, the drive mechanisms were arranged below the forging dies and to the left and to the right of the press stands. Drop forging presses for massive forming of parts in the warm state resulted in the forging dies and the drive mechanisms of the lifting beam assembly to be contaminated by forging scales and the like. To avoid such contamination, the automatic workpiece transportation apparatus was then designed for disposition above the forging die tools. Transport arms were suspended above the tools for supporting the transport beams used to grasp the workpieces.
A known mechanical linkage system including cam controls, toothed wheels and racks, and connection shafts having considerable dimensions serves to drive the movements of the transport beams in three different directions. While such a prior art mechanically operated lifting beam assembly acts reliably at the right time, such device is extremely expensive and takes up much operating space. The gears usually have a central electrical drive mechanism for all three rotatable movement shafts.
The rotational movement produced by the electrical drive mechanism is converted into translatory movement via intermediate gears, levers, cam disks, linkage systems and the like. In a known electrical drive mechanism, two gear boxes are required on respective exteriors of the press and must be mechanically synchronized with respect to each other. Such an arrangement results in a very long resilient gear chain with much play at the articulated points of the individual gear members providing an insufficiently rigid connection between the central drive and the individual movement shafts. Consequently, desired high lift-frequencies can only be utilized in an insufficient manner because of the inherent vibration in the system which allows only comparatively low speeds and the positioning accuracy in the individual movement shafts is inadequate.
The lacking flexibility of the known system viz-a-viz changes of parameters must be regarded as a further crucial disadvantage. Changes in the magnitude of movement coordination of the individual movement shafts with respect to each other and variations of speeds of movement in the individual movement shafts can only be realized at considerable expense. Such disadvantages have been endured because of the certainty of the temporarily consecutive sequences of movement of the various operations. However, with the need to adapt such lifting beam assemblies to constantly changing and smaller lot sizes of workpieces, such aggravating disadvantages can no longer be sustained.
Manipulators are known to have linkage mechanisms for carrying out various sequential operations equipped with separate electrical drive mechanisms for the individual movements. However, using electric drives for lifting beam assemblies has special difficulties. The lifting beam assembly for a drop forging press must necessarily have a sufficiently robust construction to handle the workpieces being acted upon. Consequently, the acting shafts for effectuating the mechanical movement of the lifting beam assembly must necessarily have comparatively large dimensions. Thus, individual drives for each of the movements must have sufficiently great adjusting forces to produce the controlled, fast, and at the same time harmonic movement of the individual drives. Furthermore, such individual drives must be capable of being accommodated in a specially narrowly restricted construction area. Electrical drive mechanisms are not suitable for this because of an inadequate ratio of capacity to structural volume.